Die stacking scheme

ABSTRACT

An improved die stacking scheme is provided. In accordance with one embodiment of the present invention, a multiple die semiconductor assembly is provided comprising a substrate, first and second semiconductor dies, and at least one decoupling capacitor. The first semiconductor die defines a first active surface. The first active surface includes at least one conductive bond pad. The second semiconductor die defines a second active surface, the second active surface includes at least one conductive bond pad. The first semiconductor die is interposed between the substrate and the second semiconductor die such that a surface of the second semiconductor die defines an uppermost die surface of the multiple die semiconductor assembly and such that a surface of the first semiconductor die defines a lowermost die surface of the multiple die semiconductor assembly. The decoupling capacitor is secured to the uppermost die surface and is conductively coupled to at least one of the first and second semiconductor dies.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No.09/855,731 SEMICONDUCTOR/PRINTED CIRCUIT BOARD ASSEMBLY AND COMPUTERSYSTEM, filed May 15, 2001 and Ser. No. 09/804,051 MULTIPLE DIE PACKAGE,filed Mar. 12, 2001.

The present application is also related to U.S. patent application Ser.No. 09/803,045, filed Mar. 12, 2001.

BACKGROUND OF THE INVENTION

The present invention relates to stacked multiple die semiconductorassemblies, printed circuit board assemblies, computer systems, andtheir methods of assembly. More particularly, the present inventionrelates to an improved scheme for increasing semiconductor die density.

Conventional Chip On Board (COB) techniques used to attach semiconductordies to a printed circuit board include flip chip attachment,wirebonding, and tape automated bonding (“TAB”). Flip chip attachmentconsists of attaching a flip chip to a printed circuit board or othersubstrate. A flip chip is a semiconductor chip that has a pattern orarray of electrical terminations or bond pads spaced around an activesurface of the flip chip for face down mounting of the flip chip to asubstrate. Generally, the flip chip has an active surface having one ofthe following electrical connectors: Ball Grid Array (“BGA”)—wherein anarray of minute solder balls is disposed on the surface of a flip chipthat attaches to the substrate (“the attachment surface”); SlightlyLarger than Integrated Circuit Carrier (“SLICC”)—which is similar to aBGA, but having a smaller solder ball pitch and diameter than a BGA; ora Pin Grid Array (“PGA”)—wherein an array of small pins extendssubstantially perpendicularly from the attachment surface of a flipchip. The pins conform to a specific arrangement on a printed circuitboard or other substrate for attachment thereto.

With the BGA or SLICC, the solder or other conductive ball arrangementon the flip chip must be a mirror-image of the connecting bond pads onthe printed circuit board such that precise connection is made. The flipchip is bonded to the printed circuit board by refluxing the solderballs. The solder balls may also be replaced with a conductive polymer.With the PGA, the pin arrangement of the flip chip must be amirror-image of the pin recesses on the printed circuit board. Afterinsertion, the flip chip is generally bonded by soldering the pins intoplace. An under-fill encapsulant is generally disposed between the flipchip and the printed circuit board for environmental protection and toenhance the attachment of the flip chip to the printed circuit board. Avariation of the pin-in-recess PGA is a J-lead PGA, wherein the loops ofthe J's are soldered to pads on the surface of the circuit board.

Wirebonding and TAB attachment generally begin with attaching asemiconductor chip to the surface of a printed circuit board with anappropriate adhesive, such as an epoxy. In wirebonding, bond wires areattached, one at a time, to each bond pad on the semiconductor chip andextend to a corresponding lead or trace end on the printed circuitboard. The bond wires are generally attached through one of threeindustry-standard wirebonding techniques: ultrasonic bonding—using acombination of pressure and ultrasonic vibration bursts to form ametallurgical cold weld; thermocompression bonding—using a combinationof pressure and elevated temperature to form a weld; and thermosonicbonding-using a combination of pressure, elevated temperature, andultrasonic vibration bursts. The semiconductor chip may be orientedeither face up or face down (with its active surface and bond padseither up or down with respect to the circuit board) for wire bonding,although face up orientation is more common. With TAB, ends of metalleads carried on an insulating tape such as a polyamide are respectivelyattached to the bond pads on the semiconductor chip and to the lead ortrace ends on the printed circuit board. An encapsulant is generallyused to cover the bond wires and metal tape leads to preventcontamination.

Higher performance, lower cost, increased miniaturization of components,and greater packaging density of integrated circuits are ongoing goalsof the computer industry. As new generations of integrated circuitproducts are released, the number of devices used to fabricate themtends to decrease due to advances in technology even though thefunctionality of these products increases. For example, on the average,there is approximately a 10 percent decrease in components for everyproduct generation over the previous generation with equivalentfunctionality.

In integrated circuit packaging, in addition to component reduction,surface mount technology has demonstrated an increase in semiconductorchip density on a single substrate or board despite the reduction of thenumber of components. This results in more compact designs and formfactors and a significant increase in integrated circuit density.However, greater integrated circuit density is primarily limited by thespace or “real estate” available for mounting dies on a substrate, suchas a printed circuit board.

U.S. Pat. Nos. 5,994,166 and 6,051,878, the disclosures of which areincorporated herein by reference, represent a number of schemes forincreasing semiconductor chip density on a single substrate or board.Despite the advantages of the most recent developments in semiconductorfabrication there is a continuing need for improved schemes forincreasing semiconductor die density in printed circuit boardassemblies.

BRIEF SUMMARY OF THE INVENTION

This need is met by the present invention wherein an improved diestacking scheme is provided. In accordance with one embodiment of thepresent invention, a multiple die semiconductor assembly is providedcomprising a substrate and first and second semiconductor dies. Thefirst semiconductor die includes a pair of major surfaces. One of thepair of major surfaces of the first die defines a first active surface.The other of the major surfaces of the first die defines a firststacking surface. The first active surface includes at least oneconductive bond pad. The first stacking surface is secured to thesubstrate. The second semiconductor die includes a pair of majorsurfaces. One of the pair of major surfaces of the second die defines asecond active surface. The other of the major surfaces of the second diedefines a second stacking surface. The second active surface includes atleast one conductive bon pad. The first semiconductor die iselectrically coupled to the second semiconductor die by at least onetopographic contact extending from a conductive bond pad on the secondactive surface to a conductive bond pad on the first active surface.

In accordance with another embodiment of the present invention, amultiple die semiconductor assembly is provided comprising a substrateand first and second semiconductor dies. The substrate includes a firstsurface and conductive contacts included on the first surface. The firstsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the first die defines a first active surface. Theother of the major surfaces of the first die defines a first stackingsurface. The first active surface includes at least one conductive bondpad. The first stacking surface is secured to the first surface of thesubstrate. The second semiconductor die includes a pair of majorsurfaces. One of the pair of major surfaces of the second die defines asecond active surface. The other of the major surfaces of the second diedefines a second stacking surface. The second active surface includes atleast one conductive bond pad. The first semiconductor die iselectrically coupled to the second semiconductor die by at least onetopographic contact extending from a conductive bond pad on the secondactive surface to a conductive bond pad on the first active surface. Atleast one conductive line extends from a bond pad on the first activesurface to a conductive contact on the first surface of the substrate.

In accordance with yet another embodiment of the present invention, amultiple die semiconductor assembly is provided comprising a substrateand first and second semiconductor dies. The first semiconductor dieincludes a pair of major surfaces. One of the pair of major surfaces ofthe first die defines a first active surface. The other of the majorsurfaces of the first die defines a first stacking surface. The firstactive surface includes at least one conductive bond pad. The firstactive surface is electrically coupled to the substrate by at least onetopographic contact extending from a conductive bond pad on the firstactive surface to a conductive contact on the substrate. The secondsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the second die defines a second active surface. Theother of the major surfaces of the second die defines a second stackingsurface. The second active surface includes at least one conductive bondpad. The first stacking surface is secured to the second stackingsurface.

In accordance with yet another embodiment of the present invention, amultiple die semiconductor assembly is provided comprising a substrateand first and second semiconductor dies. The substrate includes a firstsurface and conductive contacts included on the first surface. The firstsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the first die defines a first active surface. Theother of the major surfaces of the first die defines a first stackingsurface. The first active surface includes at least one conductive bondpad. The first active surface is electrically coupled to the substrateby at least one topographic contact extending from a conductive bond padon the first active surface to a conductive contact on the first surfaceof the substrate. The second semiconductor die includes a pair of majorsurfaces. One of the pair of major surfaces of the second die defines asecond active surface. The other of the major surfaces of the second diedefines a second stacking surface. The second active surface includes atleast one conductive bond pad. The first stacking surface is secured tothe second stacking surface. At least one conductive line extends from abond pad on the second active surface to a conductive contact on thefirst surface of the substrate.

In accordance with yet another embodiment of the present invention, amultiple die semiconductor assembly is provided comprising a substrate,first and second semiconductor dies, and at least one decouplingcapacitor. The first semiconductor die defines a first active surface.The first active surface includes at least one conductive bond pad. Thesecond semiconductor die defines a second active surface, the secondactive surface includes at least one conductive bond pad. The firstsemiconductor die is interposed between the substrate and the secondsemiconductor die such that a surface of the second semiconductor diedefines an uppermost die surface of the multiple die semiconductorassembly and such that a surface of the first semiconductor die definesa lowermost die surface of the multiple die semiconductor assembly. Thedecoupling capacitor is secured to the uppermost die surface and isconductively coupled to at least one of the first and secondsemiconductor dies.

In accordance with yet another embodiment of the present invention, amultiple die semiconductor assembly is provided comprising a substrate,first and second semiconductor dies, and at least one decouplingcapacitor. The first semiconductor die is positioned adjacent thesubstrate relative to the cross section. The second semiconductor die ispositioned adjacent the first semiconductor die relative to the crosssection. The first semiconductor die is interposed between the substrateand the second semiconductor die relative to the cross section. Thedecoupling capacitor is positioned adjacent the second semiconductor dierelative to the cross section and is secured to the second semiconductordie. The second semiconductor die is interposed between the decouplingcapacitor and the first semiconductor die relative to the cross section.

In accordance with yet another embodiment of the present invention, aprinted circuit board assembly is provided comprising a substrate, firstand second semiconductor dies, and a printed circuit board. The firstsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the first die defines a first active surface. Theother of the major surfaces of the first die defines a first stackingsurface. The first active surface includes at least one conductive bondpad. The first stacking surface is secured to the substrate. The secondsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the second die defines a second active surface. Theother of the major surfaces of the second die defines a second stackingsurface. The second active surface includes at least one conductive bondpad. The first semiconductor die is electrically coupled to the secondsemiconductor die by at least one topographic contact extending from aconductive bond pad on the second active surface to a conductive bondpad on the first active surface. The printed circuit board is positionedsuch that a first surface of the printed circuit board faces thesubstrate. A plurality of topographic contacts extend from the substrateto the first surface of the printed circuit board.

In accordance with yet another embodiment of the present invention, aprinted circuit board assembly is provided comprising a substrate, firstand second semiconductor dies, and a printed circuit board. The firstsemiconductor die includes a pair of major surfaces. One of the pair ofmajor surfaces of the first die defines a first active surface. Theother of the major surfaces of the first die defines a first stackingsurface. The first active surface includes at least one conductive bondpad. The first active surface is electrically coupled to the substrateby at least one topographic contact extending from a conductive bond padon the first active surface to a conductive contact on the substrate.The second semiconductor die includes a pair of major surfaces. One ofthe pair of major surfaces of the second die defines a second activesurface. The other of the major surfaces of the second die defines asecond stacking surface. The second active surface includes at least oneconductive bond pad. The first stacking surface is secured to the secondstacking surface. The printed circuit board is positioned such that afirst surface of the printed circuit board faces the substrate. Aplurality of topographic contacts extend from the substrate to the firstsurface of the printed circuit board.

In accordance with yet another embodiment of the present invention, acomputer system is provided comprising a programmable controller and atleast one memory unit. The memory unit comprises a printed circuit boardassembly according to the present invention.

In accordance with yet another embodiment of the present invention, amethod of stacking a plurality of semiconductor die is provided. Themethod comprises the steps of: providing a substrate; providing a firstsemiconductor die including a pair of major surfaces, wherein one of thepair of major surfaces of the first die defines a first active surface,the other of the major surfaces of the first die defines a firststacking surface, and the first active surface includes at least oneconductive bond pad; securing the first stacking surface to thesubstrate; providing a second semiconductor die including a pair ofmajor surfaces, wherein one of the pair of major surfaces of the seconddie defines a second active surface, the other of the major surfaces ofthe second die defines a second stacking surface, and the second activesurface includes at least one conductive bond pad; electrically couplingthe first semiconductor die to the second semiconductor die with atleast one topographic contact extending from a conductive bond pad onthe second active surface to a conductive bond pad on the first activesurface.

In accordance with yet another embodiment of the present invention, amethod of stacking a plurality of semiconductor die is provided. Themethod comprises the steps of: providing a substrate; providing a firstsemiconductor die including a pair of major surfaces, wherein one of thepair of major surfaces of the first die defines a first active surface,the other of the major surfaces of the first die defines a firststacking surface, and the first active surface includes at least oneconductive bond pad; electrically coupling the first active surface tothe substrate with at least one topographic contact extending from aconductive bond pad on the first active surface to a conductive contacton the substrate; providing a second semiconductor die including a pairof major surfaces, wherein one of the pair of major surfaces of thesecond die defines a second active surface, the other of the majorsurfaces of the second die defines a second stacking surface, and thesecond active surface includes at least one conductive bond pad; andsecuring the first stacking surface to the second stacking surface.

In accordance with yet another embodiment of the present invention, amethod of stacking a plurality of semiconductor die is provided. Themethod comprises the steps of: providing a substrate; providing a firstsemiconductor die defining a first active surface, the first activesurface including at least one conductive bond pad; providing a secondsemiconductor die defining a second active surface, the second activesurface including at least one conductive bond pad; interposing thefirst semiconductor die between the substrate and the secondsemiconductor die such that a surface of the second semiconductor diedefines an uppermost die surface of the multiple die semiconductorassembly and such that a surface of the first semiconductor die definesa lowermost die surface of the multiple die semiconductor assembly;securing at least one decoupling capacitor to the uppermost die surface;and conductively coupling the decoupling capacitor to at least one ofthe first and second semiconductor dies.

In accordance with yet another embodiment of the present invention, amethod of stacking a plurality of semiconductor die along a crosssection is provided. The method comprises the steps of: providing asubstrate; positioning a first semiconductor die adjacent the substraterelative to the cross section; positioning a second semiconductor dieadjacent the first semiconductor die relative to the cross section;interposing the first semiconductor die between the substrate and thesecond semiconductor die relative to the cross section; positioning atleast one decoupling capacitor adjacent the second semiconductor dierelative to the cross section; securing the decoupling capacitor to thesecond semiconductor die; and interposing the second semiconductor dieis between the decoupling capacitor and the first semiconductor dierelative to the cross section.

In accordance with yet another embodiment of the present invention, amethod of assembling a printed circuit board is provided. The methodcomprises the steps of: providing a substrate including first and secondsurfaces and conductive contacts included on the first surface;providing a first semiconductor die including a pair of major surfaces,wherein one of the pair of major surfaces of the first die defines afirst active surface, the other of the major surfaces of the first diedefines a first stacking surface, the first active surface includes aplurality of conductive bond pads, and the first stacking surface isdevoid of conductive bond pads; securing the first stacking surface tothe first surface of the substrate between the conductive contactsincluded on the first surface of the substrate; providing a secondsemiconductor die including a pair of major surfaces, wherein one of thepair of major surfaces of the second die defines a second activesurface, the other of the major surfaces of the second die defines asecond stacking surface, and the second active surface includes aplurality of conductive bond pads; electrically coupling the firstsemiconductor die to the second semiconductor die with a plurality oftopographic contacts extending from respective conductive bond pads onthe second active surface to a corresponding conductive bond pad on thefirst active surface; securing a single decoupling capacitor to thesecond stacking surface; providing a pair of conductive lines, each ofthe conductive lines connecting a terminal of the decoupling capacitor,a bond pad on the first active surface, and a conductive contact on thefirst surface of the substrate; electrically coupling the bond pad onthe first active surface to the second semiconductor die via one of theplurality of topographic contacts extending from respective conductivebond pads on the second active surface to a corresponding conductivebond pad on the first active surface; arranging the pair of conductivelines such that the decoupling capacitor is connected across V_(ss) andV_(cc) pins of the first and second semiconductor dies; positioning aprinted circuit board such that a first surface of the printed circuitboard faces the substrate; and providing a plurality of topographiccontacts extending from the second surface of the substrate to the firstsurface of the printed circuit board.

In accordance with yet another embodiment of the present invention, amethod of assembling a printed circuit board is provided. The methodcomprises the steps of: providing a substrate including a first surfaceand conductive contacts included on the first surface; providing a firstsemiconductor die including a pair of major surfaces, wherein one of thepair of major surfaces of the first die defines a first active surface,the other of the major surfaces of the first die defines a firststacking surface, and the first active surface includes a plurality ofconductive bond pads; electrically coupling the first active surface tothe substrate with a plurality of topographic contacts extending fromrespective conductive bond pads on the first active surface tocorresponding conductive contacts on the first surface of the substrate;providing a second semiconductor die including a pair of major surfaces,wherein one of the pair of major surfaces of the second die defines asecond active surface, the other of the major surfaces of the second diedefines a second stacking surface, the second active surface includes aplurality of conductive bond pads, and the first stacking surface isdevoid of conductive bond pads; securing the first stacking surface tothe second stacking surface; securing a single decoupling capacitor tothe second stacking surface; providing a pair of conductive lines, eachof the conductive lines connecting a terminal of the decouplingcapacitor, a bond pad on the second active surface, and a conductivecontact on the first surface of the substrate; electrically coupling theconductive contact on the first surface of the substrate to the firstsemiconductor die via one of the plurality of topographic contactsextending from respective conductive bond pads on the first activesurface to corresponding conductive contacts on the first surface of thesubstrate; arranging the pair of conductive lines such that thedecoupling capacitor is connected across V_(ss) and V_(cc) pins of thefirst and second semiconductor dies; positioning a printed circuit boardsuch that a first surface of the printed circuit board faces thesubstrate; and providing a plurality of topographic contacts extendingfrom the substrate to the first surface of the printed circuit board.

Accordingly, it is an object of the present invention to provide animproved die stacking scheme. Other objects of the present inventionwill be apparent in light of the description of the invention embodiedherein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of the preferred embodiments of thepresent invention can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 presents an illustration of a die stacking scheme according toone embodiment of the present invention;

FIG. 2 presents an illustration of a die stacking scheme according toanother embodiment of the present invention; and

FIG. 3 presents an illustration of a die stacking scheme according toyet another embodiment of the present invention.

DETAILED DESCRIPTION

Referring initially to FIG. 1, a die stacking scheme according to oneembodiment of the present invention is illustrated. FIG. 1 illustrates aprinted circuit board assembly 10. The printed circuit board assembly 10includes a multiple die semiconductor assembly 15 and a printed circuitboard 70. The multiple die semiconductor assembly 15 comprises asubstrate 20, a first semiconductor die 30, a second semiconductor die40, a decoupling capacitor 50, conductive lines 60, a plurality oftopographic contacts 80, and an encapsulant 90. It is noted that theencapsulant 90 and the semiconductor dies 30, 40 are not illustrated incross section in FIGS. 1 and 2 to preserve clarity.

The substrate 20 includes a first surface 22 and a second surface 24.Conductive contacts 82 are included on the first surface 22 and thesecond surface 24. The topographic contacts 80 extend from theconductive contacts 82 on the first and second surfaces 22, 24 of thesubstrate 20. For the purposes of defining and describing the presentinvention, it is noted that a topographic contact comprises anyconductive contact that extends between and defines a spacing between anactive surface of a substrate or die and an active surface of anothersubstrate or die. Examples include solder balls, conductive polymers, orother types of topographic electrical connections. A pin grid array,where pin recesses are provided in the opposing surface, present asuitable alternative to topographic contacts, where it is not necessaryto create a spacing between two surfaces for accommodating structurethere between.

The first semiconductor die 30 also includes a pair of major surfacesone of which defines a first active surface 32. The remaining majorsurface of the first die 30 defines a first stacking surface 34. Thefirst active surface 32 includes a plurality of conductive bond pads 84.The first stacking surface 34 is devoid of conductive bond pads and issecured to the first surface 22 of the substrate 20 between theconductive contacts 82 included on the first surface 22 of the substrate20. The first semiconductor die 30 may be secured to the substrate 20via a layer of die attach adhesive interposed between the substrate 20and the first semiconductor die 30. For the purposes of defining anddescribing the present invention, a stacking surface comprises a majorsurface of a substrate or die that is arranged to be secured to asubstrate or other generally planar assembly component. For example, asemiconductor die may be secured to a surface of a substrate byinterposing a layer of die attach adhesive between the stacking surfaceof the die and the surface of the substrate.

For the purposes of describing and defining the present invention, it isnoted that a conductive bond pad comprises a conductive surface areadefined on or extending from a surface of a semiconductor die. Aconductive contact comprises a conductive surface area defined on orextending from a substrate. An active surface comprises a surface of adie or substrate that contains conductive contacts or conductive bondpads.

The second semiconductor die 40 also includes a pair of major surfaces,one of which defines a second active surface 42. The remaining majorsurface of the second die 40 defines a second stacking surface 44. Thesecond active surface 42 includes a plurality of conductive bond pads84. The first semiconductor die 30 is electrically coupled to the secondsemiconductor die 40 by the topographic contacts 80, which extend fromrespective conductive bond pads 84 on the second active surface 42 to acorresponding conductive bond pad 84 on the first active surface 32. Thedecoupling capacitor 50 is secured to the second stacking surface 44.

Each of the pair of conductive lines 60 illustrated in FIG. 1electrically connect a terminal 52 of the decoupling capacitor 50, abond pad 84 on the first active surface 32, and a conductive contact 82on the first surface 22 of the substrate 20. The bond pad 84 on thefirst active surface 32 is electrically coupled to the secondsemiconductor die 40 via a conductive line (not shown) and one of thetopographic contacts 80 extending from a conductive bond pads 84 on thesecond active surface 42 to a corresponding conductive bond pad 84 onthe first active surface 32. In this manner, the pair of conductivelines 60 are arranged such that the decoupling capacitor may beconnected across V_(ss) and V_(cc) pins or terminals (i.e., the high andlow voltage inputs) of the first and second semiconductor dies 30, 40.It is noted that a conductive line may comprise an electricallyconductive lead, trace, bond wire, etc. In this manner, the decouplingcapacitors decouple the low voltage input from the high voltage inputand serves as a power source filter or surge/spike suppressor.

As will be appreciated by those practicing the present invention, theconductive contacts, which may embody printed conductive lines, wires,traces, and combinations thereof, electrically couple the variouscomponents of the printed circuit board assembly to the printed circuitboard and to each other. For the purposes of defining and describing thepresent invention when reference is made herein to electrical couplingto a substrate or other structure, it is understood that the electricalcoupling includes electrical coupling to a contact on a surface of thesubstrate or other structure. It is also noted that electrical couplingneed not be direct and may include coupling through one or morecircuitry components.

The printed circuit board 70 is positioned such that a first surface 72of the printed circuit board 70 faces the substrate 20. A plurality oftopographic contacts 80 extend from the second surface 24 of thesubstrate 20 to the first surface 72 of the printed circuit board 70 toelectrically couple the multiple die semiconductor assembly 15 to theprinted circuit board 70. For the purposes of describing and definingthe present invention, it is noted that a printed circuit boardcomprises a substrate upon which a circuit, network, or plurality ofelectrically conductive areas are formed.

Typically, the multiple die semiconductor assembly 15 is packaged withan encapsulant 90. Portions of the assembly may be provided withunderfill material and other packaging materials, according toconventional die packaging methodology. As will be appreciated by thosefamiliar with semiconductor fabrication, underfill materials aregenerally disposed between a die and the printed circuit board orsubstrate to which it is mounted for environmental protection and toenhance the attachment of the die to the printed circuit board orsubstrate. A die attach adhesive may be positioned to secure a die to asurface of an adjacent object and to secure an object to a surface of adie.

In,the embodiment of the present invention illustrated in FIG. 2, wherelike structure is indicated with like reference numerals, the firstactive surface 32 is electrically coupled to the substrate 20 by aplurality of topographic contacts 80 extending from respectiveconductive bond pads 84 on the first active surface 32 to correspondingconductive contacts 82 on the first surface 22 of the substrate 20. Thefirst stacking surface 34 is devoid of conductive bond pads 84 and issecured to the second stacking surface 44 with a die attach adhesive 36.The decoupling capacitor 50 is secured to the second active surface 42with, for example, a die attach adhesive (not shown). As is noted abovewith reference to the embodiment of FIG. 1, the pair of conductive lines60 are arranged such that the decoupling capacitor is connected acrossV_(ss) and V_(cc) pins or terminals (i.e., the high and low voltageinputs) of the first and second semiconductor dies. The embodiment ofFIG. 3 differs from that illustrated in FIG. 1 because both surfaces ofthe second semiconductor die 40 comprise active surfaces 42 and includeconductive bond pads 84.

Conventional stacking, soldering, bonding, under filling, encapsulating,curing, and other semiconductor processing techniques may be modifiedand arranged to yield the various stacked structures of the presentinvention. The particular fabrication steps for assembling the variousembodiments of the present invention may be gleaned from conventionalsemiconductor die stacking and packaging technology and the detaileddescription of the illustrated embodiments herein. For the purposes ofdefining the assembly scheme of the present invention it is noted thatany claims to a method of assembling a structure are not intended to belimited by the order in which specific process steps are recited in aclaim. As will be appreciated by those practicing the present invention,the printed circuit board assembly of the present invention is typicallyprovided as part of a computer system. In specific applications of thepresent invention, the semiconductor dies may form an integrated memoryunit but may embody a variety of alternative integrated circuitfunctions.

Having described the invention in detail and by reference to preferredembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention defined in the appended claims. More specifically, althoughsome aspects of the present invention are identified herein as preferredor particularly advantageous, it is contemplated that the presentinvention is not necessarily limited to these preferred aspects of theinvention.

What is claimed is:
 1. A multiple die semiconductor assembly comprising:a substrate including a first surface and conductive contacts includedon said first surface; a first semiconductor die including a pair ofmajor surfaces, wherein one of said pair of major surfaces of said firstdie defines a first active surface, the other of said major surfaces ofsaid first die defines a first stacking surface, said first activesurface includes at least one conductive bond pad, and said firststacking surface is secured to said first surface of said substrate; asecond semiconductor die including a pair of major surfaces, wherein oneof said pair of major surfaces of said second die defines a secondactive surface, the other of said major surfaces of said second diedefines a second stacking surface, said second active surface includesat least one conductive bond pad, said first semiconductor die iselectrically coupled to said second semiconductor die by at least onetopographic contact extending from a conductive bond pad on said secondactive surface to a conductive bond pad on said first active surface; atleast one decoupling capacitor secured to said second stacking surface;and at least one conductive line connecting said decoupling capacitor, abond pad on said first active surface, and a conductive contact on saidfirst surface of said substrate.
 2. A multiple die semiconductorassembly comprising: a substrate including a first surface andconductive contacts included on said first surface; a firstsemiconductor die including a pair of major surfaces, wherein one ofsaid pair of major surfaces of said first die defines a first activesurface, the other of said major surfaces of said first die defines afirst stacking surface, said first active surface includes at least oneconductive bond pad, and said first active surface is electricallycoupled to said substrate by at least one topographic contact extendingfrom a conductive bond pad on said first active surface to a conductivecontact on said first surface of said substrate; a second semiconductordie including a pair of major surfaces, wherein one of said pair ofmajor surfaces of said second die defines a second active surface, theother of said major surfaces of said second die defines a secondstacking surface, said second active surface includes at least oneconductive bond pad, and said first stacking surface is secured to saidsecond stacking surface; at least one decoupling capacitor secured tosaid second active surface; and at least one conductive line connectingsaid decoupling capacitor, a bond pad on said second active surface, anda conductive contact on said first surface of said substrate.
 3. Aprinted circuit board assembly comprising: a substrate including firstand second surfaces and conductive contacts included on said firstsurface; a first semiconductor die including a pair of major surfaces,wherein one of said pair of major surfaces of said first die defines afirst active surface, the other of said major surfaces of said first diedefines a first stacking surface, said first active surface includes aplurality of conductive bond pads, and said first stacking surface isdevoid of conductive bond pads and is secured to said first surface ofsaid substrate between said conductive contacts included on said firstsurface of said substrate; a second semiconductor die including a pairof major surfaces, wherein one of said pair of major surfaces of saidsecond die defines a second active surface, the other of said majorsurfaces of said second die defines a second stacking surface, saidsecond active surface includes a plurality of conductive bond pads, saidfirst semiconductor die is electrically coupled to said secondsemiconductor die by a plurality of topographic contacts extending fromrespective conductive bond pads on said second active surface to acorresponding conductive bond pad on said first active surface; a singledecoupling capacitor secured to said second stacking surface; a pair ofconductive lines, each of said conductive lines connecting a terminal ofsaid decoupling capacitor, a bond pad on said first active surface, anda conductive contact on said first surface of said substrate, whereinsaid bond pad on said first active surface is electrically coupled tosaid second semiconductor die via one of said plurality of topographiccontacts extending from respective conductive bond pads on said secondactive surface to a corresponding conductive bond pad on said firstactive surface, and wherein said pair of conductive lines are arrangedsuch that said decoupling capacitor is connected across V_(ss) andV_(cc) pins of said first and second semiconductor dies; a printedcircuit board positioned such that a first surface of said printedcircuit board faces said substrate; and a plurality of topographiccontacts extending from said second surface of said substrate to saidfirst surface of said printed circuit board.
 4. A printed circuit boardassembly comprising: a substrate including a first surface andconductive contacts included on said first surface; a firstsemiconductor die including a pair of major surfaces, wherein one ofsaid pair of major surfaces of said first die defines a first activesurface, the other of said major surfaces of said first die defines afirst stacking surface, said first active surface includes a pluralityof conductive bond pads, and said first active surface is electricallycoupled to said substrate by a plurality of topographic contactsextending from respective conductive bond pads on said first activesurface to corresponding conductive contacts on said first surface ofsaid substrate; a second semiconductor die including a pair of majorsurfaces, wherein one of said pair of major surfaces of said second diedefines a second active surface, the other of said major surfaces ofsaid second die defines a second stacking surface, said second activesurface includes a plurality of conductive bond pads, and said firststacking surface is devoid of conductive bond pads and is secured tosaid second stacking surface; a single decoupling capacitor secured tosaid second active surface; and a pair of conductive lines, each of saidconductive lines connecting a terminal of said decoupling capacitor, abond pad on said second active surface, and a conductive contact on saidfirst surface of said substrate, wherein said conductive contact on saidfirst surface of said substrate is electrically coupled to said firstsemiconductor die via one of said plurality of topographic contactsextending from respective conductive bond pads on said first activesurface to corresponding conductive contacts on said first surface ofsaid substrate, and wherein said pair of conductive lines are arrangedsuch that said decoupling capacitor is connected across V_(ss) andV_(cc) pins of said first and second semiconductor dies; a printedcircuit board positioned such that a first surface of said printedcircuit board faces said substrate; and a plurality of topographiccontacts extending from said substrate to said first surface of saidprinted circuit board.
 5. A multiple die semiconductor assembly asclaimed in claim 1 wherein said bond pad on said first active surface iselectrically coupled to said second semiconductor die.
 6. A multiple diesemiconductor assembly as claimed in claim 1 wherein said multiple diesemiconductor assembly further comprises an encapsulant formed over atleast a portion of said first semiconductor die, at least a portion ofsaid second semiconductor die, at least a portion of said decouplingcapacitor, and at least a portion of said substrate.
 7. A multiple diesemiconductor assembly as claimed in claim 2 wherein said conductivecontact on said first surface of said substrate is electrically coupledto said first semiconductor die.
 8. A multiple die semiconductorassembly as claimed in claim 2 wherein said multiple die semiconductorassembly further comprises an encapsulant formed over at least a portionof said second semiconductor die, at least a portion of said decouplingcapacitor, and at least a portion of said substrate.
 9. A printedcircuit board assembly comprising: a substrate including a first surfaceand conductive contacts included on said first surface; a firstsemiconductor die including a pair of major surfaces, wherein one ofsaid pair of major surfaces of said first die defines a first activesurface, the other of said major surfaces of said first die defines afirst stacking surface, said first active surface includes at least oneconductive bond pad, and said first active surface is electricallycoupled to said substrate by at least one topographic contact extendingfrom a conductive bond pad on said first active surface to a conductivecontact on said first surface of said substrate; a second semiconductordie including a pair of major surfaces, wherein one of said pair ofmajor surfaces of said second die defines a second active surface, theother of said major surfaces of said second die defines a secondstacking surface, said second active surface includes at least oneconductive bond pad, and said first stacking surface is secured to saidsecond stacking surface; at least one decoupling capacitor secured tosaid second active surface; at least one conductive line connecting saiddecoupling capacitor, a bond pad on said second active surface, and aconductive contact on said first surface of said substrate; a printedcircuit board positioned such that a first surface of said printedcircuit board faces said substrate; and a plurality of topographiccontacts extending from said substrate to said first surface of saidprinted circuit board.
 10. A computer system comprising a programmablecontroller and at least one memory unit, wherein said memory unitcomprises a printed circuit board assembly comprising: a substrateincluding a first surface and conductive contacts included on said firstsurface; a first semiconductor die including a pair of major surfaces,wherein one of said pair of major surfaces of said first die defines afirst active surface, the other of said major surfaces of said first diedefines a first stacking surface, said first active surface includes atleast one conductive bond pad, and said first stacking surface issecured to said first surface of said substrate; a second semiconductordie including a pair of major surfaces, wherein one of said pair ofmajor surfaces of said second die defines a second active surface, theother of said major surfaces of said second die defines a secondstacking surface, said second active surface includes at least oneconductive bond pad, said first semiconductor die is electricallycoupled to said second semiconductor die by at least one topographiccontact extending from a conductive bond pad on said second activesurface to a conductive bond pad on said first active surface; at leastone decoupling capacitor secured to said second stacking surface; atleast one conductive line connecting said decoupling capacitor, a bondpad on said first active surface, and a conductive contact on said firstsurface of said substrate; a printed circuit board positioned such thata first surface of said printed circuit board faces said substrate; anda plurality of topographic contacts extending from said substrate tosaid first surface of said printed circuit board.
 11. A computer systemcomprising a programmable controller and at least one memory unit,wherein said memory unit comprises a printed circuit board assemblycomprising: a substrate including a first surface and conductivecontacts included on said first surface; a first semiconductor dieincluding a pair of major surfaces, wherein one of said pair of majorsurfaces of said first die defines a first active surface, the other ofsaid major surfaces of said first die defines a first stacking surface,said first active surface includes at least one conductive bond pad, andsaid first active surface is electrically coupled to said substrate byat least one topographic contact extending from a conductive bond pad onsaid first active surface to a conductive contact on said fist surfaceof said substrate, a second semiconductor die including a pair of majorsurfaces, wherein one of said pair of major surfaces of said second diedefines a second active surface, the other of said major surfaces ofsaid second die defines a second stacking surface, said second activesurface includes at least one conductive bond pad, and said firststacking surface is secured to said second stacking surface; at leastone decoupling capacitor secured to said second active surface; at leastone conductive line connecting said decoupling capacitor, a bond pad onsaid second active surface, and a conductive contact on said firstsurface of said substrate; a printed circuit board positioned such thata first surface of said printed circuit board faces said substrate; anda plurality of topographic contacts extending from said substrate tosaid first surface of said printed circuit board.